Rough Idle?
Thread Starter
Instructor
Joined: Oct 2003
Posts: 200
Likes: 0
From: Midland Texas
Rough Idle Please Help
I have a 98 vette and it has a rough idle. I took it to the shop and they said that it is running rich but the plugs show that it is running lean. Any help on this would be great. Thanks Guys Tate
[Modified by low98vette, 4:42 AM 11/27/2003]
[Modified by low98vette, 4:42 AM 11/27/2003]
Le Mans Master
Joined: Jun 2003
Posts: 7,452
Likes: 2
From: CFOTHQlikeaMofoForums.com
St. Jude Donor '09
Re: Rough Idle? (low98vette)
:seeya Welcome
I've heard that a rough idle can be caused by the plugs, w/ the little platinum pucks falling off and widening the gap. I've got the same thing and will be replacing all 8 plugs shortly w/ NGKs to try and correct it :smash:
:crazy: Ride On ;)
I've heard that a rough idle can be caused by the plugs, w/ the little platinum pucks falling off and widening the gap. I've got the same thing and will be replacing all 8 plugs shortly w/ NGKs to try and correct it :smash:
:crazy: Ride On ;)
Le Mans Master
Joined: Oct 1999
Posts: 8,205
Likes: 40
From: Tucson AZ
Re: Rough Idle Please Help (low98vette)
Welcome to the Forum. It could be many things including plugs, wires, carbon build-up, IAC valve, etc. I think there is an upgrade to your PCM program that will address this too; ask your dealer. :yesnod: :)
Instructor
Joined: Jan 2003
Posts: 119
Likes: 0
From: Bloomingdale IL
Re: Rough Idle Please Help (low98vette)
I had the same problem, it turned out to be a wire. If your going to do the plugs, replace the wires at the same time. It's cheap and it won't take you any longer. :cheers:
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Thread Starter
Instructor
Joined: Oct 2003
Posts: 200
Likes: 0
From: Midland Texas
Re: Rough Idle Please Help (low98vette)
How did you find out it was a coil? :confused: I replaced the plugs and wires today. It seemed to have eased the roughness a little, but it still idles at about 600 rpm. This is going to drive me crazy :banghead:
[Modified by low98vette, 8:08 PM 11/28/2003]
[Modified by low98vette, 8:08 PM 11/28/2003]
Team Owner
Joined: Mar 1999
Posts: 28,753
Likes: 9
From: San Jose/Bear Valley CA
CA Events Coordinator
Re: Rough Idle Please Help (low98vette)
Hookup a Timing light to the plug wire, then look for a steady beat of light... the one that does not have a steady beat is the bad coil... :yesnod:
VR :cheers:
VR :cheers:
Drifting
Joined: Sep 2002
Posts: 1,265
Likes: 0
From: Austin Texas
Re: Rough Idle Please Help (low98vette)
I have a 99 vette, and it has a rough idle also. I am goin to try to clean the TB, then check the coils
I had already did a decarb. plugs, and new wires.
no luck
I had already did a decarb. plugs, and new wires.
no luck
Racer
Joined: Aug 2003
Posts: 290
Likes: 8
From: 60 miles from BGKY
Re: Rough Idle Please Help (low98vette)
Have you checked out some of the other threads on this? It is entirely possible it's a characteristic of the cam. My 98 (bought it with 50K) has a slightly rough idle at times too. For grins, I swapped the original platinum plugs (looked great, no missing pucks) for a set of Delco Iridiums and added a set of MSD wires. No change. Prior to this, I had only swapped out the airbox (for a Blackwing), put on a friend's Granatelli MAF, and added a set of Borla's. Idle always the same after each mod, which I kinda expected.
I hooked it up to AutoTap yesterday, and there is nothing wrong--no codes, no misfires, nada. I don't mind the idle, but reading other threads got me curious if there was an ignition/other problem. Nope. Peace of mind, and $100 bucks for a nice upgrade I wanted to do anyway.
By all means check the suggestions out. If you have a friend with AutoTap or another analyzer, hook it up before spending $$ on things you may not need. Let us know how it goes!
I hooked it up to AutoTap yesterday, and there is nothing wrong--no codes, no misfires, nada. I don't mind the idle, but reading other threads got me curious if there was an ignition/other problem. Nope. Peace of mind, and $100 bucks for a nice upgrade I wanted to do anyway.
By all means check the suggestions out. If you have a friend with AutoTap or another analyzer, hook it up before spending $$ on things you may not need. Let us know how it goes!
Team Owner
Joined: Mar 1999
Posts: 28,753
Likes: 9
From: San Jose/Bear Valley CA
CA Events Coordinator
Re: Rough Idle Please Help (LivinTheDream)
Funny thing I learned is that the coils can be bad enough to make the car run like garbage but not bad enough to throw a code... All along I was told by the dealership that if the coil was bad... it would throw a code. :rolleyes: Once I installed the new coil in place of the bad one... the car ran smooth as silk.
I spent 3 years with a high priced car that ran like garbage. :mad I took an engine building shop about 15 min to find my problem. Once you change your plugs and wires... Check the coils... it could be your entire problem.
VR :cheers:
I spent 3 years with a high priced car that ran like garbage. :mad I took an engine building shop about 15 min to find my problem. Once you change your plugs and wires... Check the coils... it could be your entire problem.
VR :cheers:
Drifting
Joined: Sep 2002
Posts: 1,265
Likes: 0
From: Austin Texas
Re: Rough Idle Please Help (vetterdstr)
I cleaned the TB today and decarbed the motor, still rough idle for me also.
I hooked up a timing light to each wire but couldn't really see any difference. how did the shop determine yours, was it a really noticable difference?
I hooked up a timing light to each wire but couldn't really see any difference. how did the shop determine yours, was it a really noticable difference?
Team Owner
Joined: Mar 1999
Posts: 28,753
Likes: 9
From: San Jose/Bear Valley CA
CA Events Coordinator
Re: Rough Idle Please Help (99 torch red vette)
When a coil is firing correctly the light will flash steady. If the coil is not working correctly it will flash steady then skip a beat... you will have to watch each one flash for 15 seconds or so to be sure they are firing correctly.
VR
VR
Thread Starter
Instructor
Joined: Oct 2003
Posts: 200
Likes: 0
From: Midland Texas
Re: Rough Idle Please Help (low98vette)
The Chevy house said that there was 1280 missfifes in the history when they hooked it up to the computer. They said that everything was fine now. I am going to try the timing light fix today. Thanks for all the help guys. Tate :steering:
Le Mans Master
Joined: Apr 2002
Posts: 6,927
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From: Glendale NY
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18- '19
Re: Rough Idle Please Help (low98vette)
++++++++ The Chevy house said that there was 1280 missfifes in the history when they hooked it up to the computer. They said that everything was fine now. I am going to try the timing light fix today. Thanks for all the help guys. Tate ++++++++++++++++++++++++++++++++++++++
Let us know how you make out. 1280 misfires doesn't sound like a lot when you think about how many times the engine actually fires. I'm going to try the timing light thing myself.......as soon as I get mine back. I hate loaning things out and then when I need it.....I don't have it. Today would have been a perfect time to do this.
Let us know how you make out. 1280 misfires doesn't sound like a lot when you think about how many times the engine actually fires. I'm going to try the timing light thing myself.......as soon as I get mine back. I hate loaning things out and then when I need it.....I don't have it. Today would have been a perfect time to do this.
